Philippine President Rodrigo Duterte has decided to declare a lagoon in China-controlled waters to be a marine sanctuary where Filipinos and Chinese will be prohibited from fishing, officials said Monday. China seized the Scarborough Shoal in 2012 after a tense standoff with the Philippines. Duterte’s plan is delicate because it may imply Philippine territorial control there. Chinese coast guard ships have closely guarded the shoal since then, and both governments have suspected the other of planning construction to cement their claims to the area.

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If Duterte’s plan proceeds, fishermen of any nationality would only be allowed in the deeper waters just outside Scarborough, but not its vast triangular-shaped lagoon naturally fenced by coral outcrops with an entryway watched by Chinese coast guard personnel.

Duterte relayed his marine sanctuary plan to Chinese President Xi Jinping during a meeting on the sidelines of the just-concluded Asia Pacific Economic Cooperation forum in Peru, National Security Adviser Hermogenes Esperon Jr. said. Xi did not say whether he agreed to Duterte’s plan in the Scarborough Shoal, according to the statement from Esperon and other Philippine Cabinet officials present at the meeting.

“It is our position not to have fishing activities inside the triangle,” Esperon said of Scarborough’s shallow lagoon. “The president has decided to declare that as a sanctuary. That is a unilateral action from government.”

“If they don’t want to allow fishing there, we don’t want to allow fishing there either,” Esperon said of the countries’ similar but separate regulations in the disputed area. The Philippine government is considering declaring other disputed South China Sea areas as government-protected marine sanctuaries, according to Esperon.

After taking control of Scarborough, which lies about 228 kilometers (123 nautical miles) off the northwestern Philippines, Chinese coast guard personnel shooed away Filipino fishermen, at times with the use of water cannons or by deploying armed personnel on speed boats to chase them off.

Duterte’s predecessor, Benigno Aquino III, responded by bringing the shoal dispute and other territorial issues against China to international arbitration. An international tribunal ruled in July against China, saying it violated the Filipinos’ rights by banning them from fishing. China, however, ignored the ruling, which also invalidated its vast claims to virtually all of the South China Sea. Duterte, who took office in June, reversed his predecessor’s adversarial stance and reached out to China.

Shortly after Duterte discussed the Scarborough dispute with Xi in a state visit to Beijing, Filipinos were allowed to return to the shoal to fish. Philippine coast guard ships also resumed patrols in the vicinity of the shoal.

While the territorial disputes persist, China and the Philippines have signed about 20 trade and economic agreements. China has also sent officials to meet Filipino fishermen, who were displaced by the rift over Scarborough, to find ways of helping them, Esperon said, explaining how Duterte’s approach has reaped immediate benefits.

“Remember that in our relations with China, the sum total is not Scarborough,” he said.